unmannable

unmannableadj.— «A new word is entering the aero space lexicon as the US Air Force analyses its long-range strike options—unmannable: an aircraft that could begin its life manned, then evolve over time to unmanned operation; or one that could switch between missions, flying unmanned when the persistence required or threat faced is beyond a manned aircraft.» —“Farnborough review: Pilot optional” by Graham Warwick Flight (Sutton, United Kingdom) Aug. 1, 2006. (source: Double-Tongued Dictionary)